When you charge at home at a home charging point, the data from your home charging session is stored in the device. At the same time, the device communicates via internet with the Charge Point Operator (CPO), e.g. Blue Corner.
When the connection is poor or lost, it is possible that the CPO does not have all the data at that moment to make a full refund. Thus, there may also be a difference between what you are refunded and what you find (later) in the CPO portal or app. Stored data from a home loading session are not lost, however. Once the internet connection is there again, the home charger will send the missing data. The next refund will then include these missing sessions.